A chronic, low-dose regimen of the antiprogestin ZK 137 316 prevents pregnancy in rhesus monkeys

ISSN： 1460-2350

Source： Human Reproduction, Vol.13, Iss.8, 1998-08, pp. : 2132-2138

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Abstract

Continual administration of low doses of the antiprogestin ZK 137 316 was previously reported to permit ovarian/menstrual cyclicity, but disrupt endometrial growth in macaques. The contraceptive efficacy of this regimen was tested in female rhesus monkeys (10 per group) treated daily with vehicle (controls), 0.01 or 0.03 mg ZK 137 316 per kg body weight for 30 days before and during continual co-habitation with males of proven fertility. Treatment continued until confirmation of pregnancy or for 5 months after pair-housing with males. Mating and vaginal sperm were evident in all females. A cumulative pregnancy rate of 90% (9/10) was observed in the controls. Of the 10 animals receiving 0.01 mg/kg, four conceived during the first 2 months of pairing (P = 0.06) with no further conceptions. No pregnancies were observed in the 0.03 mg/kg group (P < 0.01).="" timely,="" overt="" menses="" occurred="" at="" a="" higher="" frequency="" in="" the="" 0.01="" mg/kg="" group="" than="" the="" 0.03="" mg/kg="" group.="" however,="" corpora="" lutea="" were="" present="" in="" ovaries="" from="" both="" groups="" during="" the="" last="" treatment="" cycle,="" indicating="" that="" ovarian="" cycles="" occurred.="" thus,="" chronic="" administration="" of="" low-dose="" zk="" 137="" 315="" that="" permits="" continued="" ovarian="" cyclicity="" and="" a="" high="" incidence="" of="" timely="" menses,="" prevents="" pregnancy="" in="" non-human="" primates.="" this="" regimen="" may="" provide="" a="" novel="" method="" of="" contraception="" for=""> Keywords:antiprogestin/contraception/menstrual cycle/pregnancy/ZK 137 316